The present invention relates to a method for making a life vest and, more particularly, to a method for making a life vest having two double-knitted fabrics to shorten the processing time, to increase the thickness of the fabrics, to increase the processing efficiency, and to reduce the labor hours and the material costs.
FIGS. 1-3 show a conventional life vest 9 and FIG. 4 shows a method for making the life vest. The life vest 9 includes two rubber sponge sheets 91 and 92 and a buoyant material 97 between the rubber sponge sheets 91 and 92. Each rubber sponge sheet 91, 92 include two fabrics 93 and 94 and a rubber sponge 97 sandwiched between the fabrics 93 and 94. The buoyant material 97 is sandwiched between the fabrics 93 and 94. The fabrics 93 and 94 are prepared by weaving or knitting (see 901). The fabrics 93 and 94 are then treated with a dyeing process (see 902). Thereafter, a rubber sponge 95 is sandwiched between the dyed fabrics 93 and 94 in a lamination process (see 903) to form the rubber sponge sheets 91 and 92. The rubber sponge sheets 91 and 92 are cut and sewed, so that the buoyant material 97 is filled between the rubber sponge sheets 91 and 92 in each sewing area 96 to form the life vest 9. The rubber sponge 95 is elastic and hydrophobic and, thus, has long been the best choice for making the life vest 9. However, the life vest 9 is not permeable to air, so that the wearer feels hot and uncomfortable. Furthermore, the rubber sponge 95 is liable to become flimsy and has odor and causes environmental pollution after they are discarded. Furthermore, the yield of the life vest 9 is low if the quality control in the lamination process is poor.
To overcome the disadvantages of the life vest 9, U.S. Pat. No. 7,024,891 discloses a method for making a life vest includes knitting or weaving, dyeing, and sewing. In the knitting or weaving, a material including synthetic filament synthetic  monofilament and elastic yarn is combined by a double weft knitting machine to make a textile for the life vest. However, the knitting or weaving process is complicated, slow, and expensive. Furthermore, the elastic yarn in the life vest still has the tendency of becoming flimsy.
Thus, a need exists for an improved method for making a life vest without the disadvantages of conventional life vests.